Processes for recovering tantalum and niobium with carbon tetrachloride

ABSTRACT

There is provided a method of treating solid material, wherein the solid material includes target metallic material and one or more other metallic elements, wherein the target metallic material consists of at least one of tantalum and niobium, the method comprising contacting the solid material with a gaseous reagent material within a reaction zone, wherein the gaseous reagent material includes carbon tetrachloride.

FIELD

The present disclosure relates to processes for recovering tantalum and niobium, such as, for example, from ores, such as coltan.

BACKGROUND

Traditional methods for separating tantalum and niobium from ores are high temperature processes, which do not lend themselves to separating tantalum and niobium from ores such as coltan, which include naturally occurring radioactive elements, as separation of such radioactive elements from the tantalum and niobium is relatively difficult under these processing conditions.

SUMMARY

In one aspect, there is provided a method of treating solid material, wherein the solid material includes target metallic material and one or more other metallic elements, wherein the target metallic material consists of at least one of tantalum and niobium, the method comprising contacting the solid material with a gaseous reagent material within a reaction zone, wherein the gaseous reagent material includes carbon tetrachloride.

In another aspect, there is provided a method of reducing niobium chloride comprising contacting niobium chloride with aluminium.

In a further aspect, there is provided a method of reducing tantalum chloride comprising contacting tantalum chloride with aluminium.

BRIEF DESCRIPTION OF DRAWINGS

The preferred embodiments of the process will now be described with reference to the following accompanying drawings, in which:

FIG. 1 is a flowsheet illustrating an embodiment of the process;

FIG. 2 is a flowsheet illustrating another embodiment of the process; and

FIG. 3 is a schematic illustration of the experimental set-up for Example 1.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, there is provided a process 10 (110) of treating solid material 12. In some embodiments, for example, the solid material includes solid particulate material. In some of these embodiments, for example, at least 90 weight % of the solid particulate material has a diameter of less than one millimetre.

In some embodiments, for example, the solid material is an ore, such as coltan ore, a concentrate, or any other solid metal-comprising material. In some embodiments, for example, the solid material is derived from an ore, such as coltan ore. In some embodiments, for example, the ore is dried and subjected to size reduction (for example, by crushing, drying, milling and/or grinding) prior to being subjected to the treatment of the process.

The solid material includes target metallic material and one or more other metallic elements.

The target metallic material consists of at least one of tantalum and niobium. In some embodiments, for example, the target metallic material consists of tantalum. In some embodiments, for example, the target metallic material consists of niobium. In some embodiments, for example, the target metallic material consists of both of tantalum and niobium. In some embodiments, for example, the tantalum includes, and in some of these embodiments, consists of tantalum that is present in one or more oxides of tantalum, or one or more compounds of tantalum. In some of these embodiments, for example, the niobium includes, and in some of these embodiments, consists of, niobium that is present in one or more oxides of niobium, or one or more compounds of niobium. In some embodiments, for example, the solid material includes between 5 weight % and 40 weight % tantalum, based on the total weight of the solid material.

In some embodiments, for example, the solid material includes between 1 weight % and 40 weight % niobium, based on the total weight of the solid material. In some embodiments, for example, the solid material includes between 10 weight % and 80 weight % target metallic material, based on the total weight of the solid material.

In some embodiments, for example, the one or more other metallic elements include at least one of iron, tin, and titanium. In some embodiments, for example, the one or more other metallic elements include one or more naturally occurring radioactive elements. In some of these embodiments, for example, the one or more naturally occurring radioactive elements includes at least one of uranium and thorium. In some embodiments, for example, the solid material includes between 0.01 weight % and 0.5 weight % naturally occurring radioactive elements, based on the total weight of the solid material.

Referring to FIG. 1, in one embodiment of the process, the process 10 comprises contacting the solid material 12 with a gaseous reagent material 14 within a reaction zone 16 to effect production of a gaseous reaction product 18 and a depleted solid material, wherein the gaseous reagent material includes carbon tetrachloride.

Any naturally occurring radioactive elements, that are disposed within the solid material, do not, or at least not to any significant degree, participate in any reactive process to effect their depletion from the solid material 12, such that most, if not all, of the naturally occurring radioactive elements remain in the depleted solid material after the contacting.

In some embodiments, for example, the reaction zone 16 is disposed at a temperature of less than 500 degrees Celsius. In some embodiments, for example, the reaction zone 16 is disposed at a temperature of between 300 degrees Celsius and 500 degrees Celsius. In some embodiments, for example, the reaction zone is disposed at a pressure of between 7 bar and 12 bar.

In some embodiments, for example, the gaseous reagent material 14 includes at least 40 mol % carbon tetrachloride, based on the total moles of the gaseous reagent material. In some embodiments, for example, the gaseous reagent material 14 is supplied to the reaction zone 16. In some embodiments, for example, the carbon tetrachloride is generated in-situ within the reaction zone 16.

In some embodiments, for example, within the reaction zone 16, the ratio of moles of the carbon tetrachloride to moles of the target metallic material is at least 2.5. In some embodiments, for example, within the reaction zone, the ratio of moles of the carbon tetrachloride to moles of the target metallic material is between 2.5 and 5.

In some embodiments, for example, the solid material 12 consists of the target metallic material and other material, and wherein the contacting effects production of a gaseous reaction product, wherein the ratio of moles of the target metallic material within the gaseous reaction product to moles of the other material within the gaseous reaction product is greater than the ratio of moles of the target metallic material within the solid material to moles of the other material within the solid material. In some of these embodiments, for example, the ratio of moles of the target metallic material within the gaseous reaction product to moles of the other material within the gaseous reaction product is greater than the ratio of moles of the target metallic material within the solid material to moles of the other material within the solid material by a multiple of at least 2.

Referring to FIG. 1, in some embodiments, for example, the process 10 further includes separating, from the gaseous reaction product 18, a target metallic material-rich product 20 and a target metallic material-lean product 22, based on differences in volatility as between the target metallic material-rich product and the target metallic material-lean product. In some embodiments, for example, the separating is effected after the reaction in the reaction zone 16 has been substantially completed (for example, 30 minutes after commencement of the reaction), and after the gaseous reaction product 18 has been vented from the reaction zone 16. The concentration of the target metallic material within the target metallic material-rich product 20 is greater than the concentration of the target metallic material within the target metallic material-lean product 22.

Again referring to FIG. 1, in some embodiments, for example, the method further includes separating, from the gaseous reaction product 18, a target metallic material-rich product 20, based on differences in volatility as between the target metallic material-rich product 20 and a residue, deriving from the gaseous reaction product, whose production is also effected by the separating. The concentration of the target metallic material within the target metallic material-rich product 20 is greater than the concentration of the target metallic material within the residue.

In some embodiments, for example, the separating, from the gaseous reaction product 18, of a target metallic material-rich product 20 and a target metallic material-lean product 22 (or a residue), based on differences in volatility as between the target metallic material-rich product and the target metallic material-lean product (or the residue, as the case may be), includes cooling the gaseous reaction product in a cooling zone 24 so as to effect desublimation of at least a fraction of the gaseous reaction product and effect production of a desublimed product 26. In some embodiments, for example, the cooling zone 24 is disposed at a temperature of between 80 degrees Celsius and 100 degrees Celsius, and at atmospheric pressure. In some embodiments, after the desublimation, at least a fraction of the gaseous reaction product remains gaseous, and such fraction is discharged as an off-gas. In some embodiments, for example, the off-gas is cooled to remove excess carbon tetrachloride, and such excess carbon tetrachloride can be recycled to the reaction zone 16. Any remaining gaseous material, after this cooling step, can be combusted.

The desublimed product is heated in a heating zone 28 so as to effect sublimation of at least a fraction of the solidified desublimed product and thereby effect production of a sublimed product 30 and a residue. In some embodiments, for example, the heating zone 28 is disposed at a temperature of between 150 degrees Celsius and 300 degrees Celsius, and at atmospheric pressure. The sublimed product 30 includes, or consists of the target metallic material-rich product 20. The residue 32 includes, or consists of, the target metallic material-lean product 22. In some embodiments, for example, the gaseous reaction product 18 includes iron chloride, and the residue 32 includes iron.

Referring to FIG. 1, in some embodiments, for example, the sublimed product 30 is supplied to a fractional distillation unit operation 34, and the sublimed product is fractionated by distillaton into a tantalum-rich separation product 36 and a niobium-rich separation product 38. The tanatalum-rich separation product includes tantalum in the form of tantalum chloride. The niobium-rich separation product includes niobium in the form of niobium chloride. The tantalum-rich separation product is a more volatile fraction (“lighter”) than the niobium-rich separation product. In some embodiments, for example, further heavier and lighter streams are separated from the sublimed product. In some embodiments, for example, a more volatile separation product, including tin and titanium chlorides, and more volatile than both of the tantalum-rich separation product and the niobium-rich separation product, is recovered. In some embodiments, for example, the fractional distillation unit operation 34 is operated within a temperature range of between 200 degrees Celsius and 400 degrees Celsius, and at atmospheric pressure.

Referring to FIG. 1, in some embodiments, for example, each one of the tantalum-rich separation product 36 and the niobium-rich separation product 38, independently, is contacted with aluminium. Contacting the tantalum-rich separation product 36 with aluminium in a first reaction zone 40 effects reduction of tantalum and thereby effect production of tantalum metal. Contacting the niobium-rich separation product 38 with aluminium in a second reaction zone 42 effects reduction of niobium and thereby effect production of niobium metal. In some embodiments, for example, both of the first and second reaction zones 40, 42 are disposed at a temperature of between 500 degrees Celsius and 800 degrees Celsius, and at atmospheric pressure.

The contacting, in each case, also effects production of aluminium chloride. In some of these embodiments, for example, the aluminium chloride is recovered and further processed to effect recovery of chlorine, and then the chlorine is further processed to effect production of carbon tetrachloride for contacting with the solid material of the process.

Referring to FIG. 2, another embodiment of process, process 110, is provided. The process 110 comprises contacting the solid material 102 with a gaseous reagent material 104 within a reaction zone 106 to effect production of a gaseous reaction product and a depleted solid material, wherein the gaseous reagent material includes carbon tetrachloride.

Any naturally occurring radioactive elements, that are disposed within the solid material, do not, or at least not to any significant degree, participate in any reactive process to effect their depletion from the solid material 102, such that most, if not all, of the naturally occurring radioactive elements remain in the depleted solid material after the contacting.

In some embodiments, for example, the reaction zone 106 is disposed at a temperature of less than 500 degrees Celsius. In some embodiments, for example, the reaction zone 106 is disposed at a temperature of between 300 degrees Celsius and 500 degrees Celsius. In some embodiments, for example, the reaction zone is disposed at a pressure of between 7 bar and 12 bar.

In some embodiments, for example, the gaseous reagent material 104 includes at least 40 mol % carbon tetrachloride, based on the total moles of the gaseous reagent material. In some embodiments, for example, the gaseous reagent material 104 is supplied to the reaction zone 106. In some embodiments, for example, the carbon tetrachloride is generated in-situ within the reaction zone 106.

In some embodiments, for example, within the reaction zone 106, the ratio of moles of the carbon tetrachloride to moles of the target metallic material is at least 2.5. In some embodiments, for example, within the reaction zone, the ratio of moles of the carbon tetrachloride to moles of the target metallic material is between 2.5 and 5.

In some embodiments, for example, the solid material 102 consists of the target metallic material and other material, and wherein the contacting effects production of a gaseous reaction product, wherein the ratio of moles of the target metallic material within the gaseous reaction product to moles of the other material within the gaseous reaction product is greater than the ratio of moles of the target metallic material within the solid material to moles of the other material within the solid material. In some of these embodiments, for example, the ratio of moles of the target metallic material within the gaseous reaction product to moles of the other material within the gaseous reaction product is greater than the ratio of moles of the target metallic material within the solid material to moles of the other material within the solid material by a multiple of at least 2.

In some embodiments, for example, after the reaction has been substantially completed (for example, 30 minutes after commencement of the reaction), the reaction zone is cooled down below 100 degrees Celsius to effect desublimation of the gaseous reaction product, and remaining off-gases are vented for carbon tetrachloride recovery (as described above with respect to the embodiment illustrated in FIG. 1). The reactor is then heated to between 400 degrees Celsius and 700 degrees Celsius to effect sublimation of the desublimed product and thereby effect production of sublimed product 108.

The sublimed product 108 is discharged from the reaction zone 106, and is supplied to an absorption unit operation 112. The sublimed product 108 consists of target metallic material and other material. The absorption unit operation 112 preferentially absorbs the other material, relative to the target metallic material, such that a gaseous target metallic material-rich absorption unit product 114 is produced by the absorption unit operation. The concentration of target metallic material is greater within the target metallic material-rich absorption unit product 114 than within the sublimed product 108.

In some embodiments, for example, the absorption unit operation 112 is an absorber including solid absorbent media including sodium chloride or any one or more other alkaline chlorides. The sublimed product 108 is flowed across the solid absorbent media to effect contacting between the sublimed product 108 and the solid absorbent media. The contacting effects a reactive process, and at least a fraction of the sublimed product 108 is consumed during the reactive process to effect production of an absorption unit reaction product that becomes disposed on the absorbent and thereby removed from the sublimed product 108 so as to effect production of the gaseous target metallic material-rich absorption unit product 114. In some embodiments, for example, the other material includes iron, and the gaseous reaction product includes iron chloride, and the absorption unit reaction product includes NaFeCl₄. In some embodiments, for example, the absorber is operated at a temperature of between 400 degrees Celsius and 700 degrees Celsius, and at atmospheric pressure.

In some embodiments, for example, the absorbed NaFeCl₄ is stripped from the solid media absorbent and then processed for effecting recovery of the chlorine, which can then be further processed to produce carbon tetrachloride, which then can be used for contacting the solid material of the process 110. In some embodiments, for example, multiple absorbers are provided so that, while one absorber is receiving the sublimed product 108, another absorber is operating in a regeneration mode, having previously absorbed NaFeCl₄ stripped from the solid media adsorbent so as to regenerate the solid media absorbent for contacting with the sublimed product 108.

The target metallic material-rich absorption unit product 114 is supplied to a fractional distillation unit operation 116, and the target metallic material-rich absorption unit product is fractionated by distillaton into a tantalum-rich separation product 118 and a niobium-rich separation product 120. The tanatalum-rich separation product 118 includes tantalum in the form of tantalum chloride. The niobium-rich separation product 120 includes niobium in the form of niobium chloride. The tantalum-rich separation product 118 is a more volatile fraction (“lighter”) than the niobium-rich separation product 120. In some embodiments, for example, further heavier and lighter streams are separated from the target metallic material-rich absorption unit product. In some embodiments, for example, a more volatile separation product, including tin and titanium chlorides, and more volatile than both of the tantalum-rich separation product and the niobium-rich separation product, is recovered. In some embodiments, for example, the fractional distillation unit operation 116 is operated within a temperature range of between 200 degrees Celsius and 400 degrees Celsius, and at atmospheric pressure.

Referring to FIG. 1, in some embodiments, for example, each one of the tantalum-rich separation product 118 and the niobium-rich separation product 120, independently, is contacted with gaseous hydrogen. Contacting the tantalum-rich separation product 118 with gaseous hydrogen in a first reaction zone 122 effects reduction of tantalum and thereby effect production of tantalum metal. Contacting the niobium-rich separation product 120 with gaseous hydrogen in a second reaction zone 124 effects reduction of niobium and thereby effect production of niobium metal. In some embodiments, for example, both of the first and second reaction zones 122, 124 are disposed at a temperature of between 900 degrees Celsius and 1500 degrees Celsius, and at atmospheric pressure.

Both contacting steps effect production of gaseous hydrochloric acid. In some embodiments, for example, the gaseous hydrochloric acid is recovered and further processed to recover chlorine, and the recovered chlorine is further processed to effect production of carbon tetrachloride which can be used for contacting of the solid material of the process.

Further embodiments will now be described in further detail with reference to the following non-limitative example.

Example

50 g of coltan ore containing 3.96% niobium, 19.15% tantalum, and 15.67% iron, each based on the total weight of coltan ore, was charged to a horizontal reactor 310 as shown in the FIG. 3. The reactor was heated to 450° C., and then the needle valve, separating the CCl₄ holding reactor 312 and the horizontal reactor 310, was opened, and CCl₄ was allowed to pass through the horizontal reactor 310, containing a flat bed of coltan, very slowly. The reactor 310 was closed when the pressure reached 60-80 psi, and left 30 minutes to react. Then the pressure build up was released to pass through the de-sublimation tube 314. There was significant amount of yellow and brown de-sublimation observed with liquid CCl₄. This procedure was repeated for five times and the test was stopped to analyze the residue (hereinafter, the “chloride” mixture”) in the reactor 310. Table 1 illustrates the mass balance of the test. 99% of Tantalum, 99% of the Niobium and 63% of the Iron was extracted from the initial charge.

TABLE 1 Mass Balance Tantalum Niobium Iron Grams grams % Grams % grams % Feed 50.0 9.58 19.15% 1.98 3.96% 7.84 15.67% Resi- 19.6 0.10  0.53% 0.02 0.10% 2.94 14.98% due 9.47   99% 1.96   99% 4.90   63%

The resultant product was free of any radioactive material.

The chloride mixture was stored under argon, and used for further refining steps. The mixture was transferred under argon to a sublimation apparatus, and sublimed to produced niobium and tantalum chlorides. The chlorides were permitted to de-sublime on the wall, and were then collected and analyzed. Analysis showed only niobium and tantalum chlorides present in the de-sublimed material. The remains at the bottom of the sublimation beaker included mainly iron chloride. The tantalum and niobium chlorides were then distilled out and then reduced with aluminium to produce niobium and tantalum metals.

While this invention has been described with reference to illustrative embodiments and examples, the description is not intended to be construed in a limiting sense. Thus, various modifications of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to this description. It is therefore contemplated that the appended claims will cover any such modifications or embodiments. Further, all of the claims are hereby incorporated by reference into the description of the preferred embodiments. 

1. A method of treating solid material, wherein the solid material includes target metallic material and one or more other metallic elements, wherein the target metallic material consists of at least one of tantalum and niobium, the method comprising contacting the solid material with a gaseous reagent material within a reaction zone, wherein the gaseous reagent material includes carbon tetrachloride.
 2. The method as claimed in claim 1, wherein the target metallic material consists of tantalum.
 3. The method as claimed in claim 1, wherein the target metallic material consists of niobium.
 4. The method as claimed in claim 1, wherein the target metallic material consists of tantalum and niobium.
 5. The method as claimed in any one of claims 1 to 4, wherein the solid material includes solid particulate material.
 6. The method as claimed in any one of claims 1 to 4, wherein the solid material is solid particulate material, and wherein at least 90 weight % of the solid particulate material has a diameter of less than one millimetre.
 7. The method as claimed in any one of claim 1, 2, 4, 5, or 6, wherein the tantalum includes tantalum that is present in one or more oxides of tantalum.
 8. The method as claimed in any one of claim 1, 3, 4, 5, 6, or 7, wherein the niobium includes niobium that is present in one or more oxides of niobium.
 9. The method as claimed in any one of claim 1, 2, 4, 5, or 6, wherein the tantalum consists of tantalum that is present in one or more oxides of tantalum.
 10. The method as claimed in any one of claim 1, 3, 4, 5, 6, or 8, wherein the niobium consists of niobium that is present in one or more oxides of niobium.
 11. The method as claimed in any one of claims 1 to 10, wherein the one or more other metallic elements include one or more naturally occurring radioactive elements.
 12. The method as claimed in claim 11, wherein the one or more naturally occurring radioactive elements include at least one of uranium and thorium.
 13. The method as claimed in any one of claim 1, 2, 4, 5,
 6. 7, 9, 11, or 12, or, so long as the target metallic material includes tantalum, any one of claims 8 and 10, wherein the solid material includes between 5 weight % and 40 weight % tantalum, based on the total weight of the solid material.
 14. The method as claimed in any one of claim 1, 3, 4, 5, 6, 8, 10, 11, 12, or 13, or, so long as the target metallic material includes niobium, any one of claim 7 or 9, wherein the solid material includes between 1 weight % and 40 weight % niobium, based on the total weight of the solid material.
 15. The method as claimed in any one of claims 1 to 14, wherein the solid material includes between 10 weight % and 80 weight % target metallic material, based on the total weight of the solid material.
 16. The method as claimed in any one of claims 1 to 15, wherein the solid material includes between 0.01 weight % and 0.5 weight % naturally occurring radioactive elements, based on the total weight of the solid material
 17. The method as claimed in any one of claims 1 to 16, wherein the solid material is derived from coltan ore.
 18. The method as claimed in any one of claims 1 to 17, wherein the reaction zone is disposed at a temperature of less than 400 degrees Celsius.
 19. The method as claimed in any one of claims 1 to 17, wherein the reaction zone is disposed at a temperature of between 150 degrees Celsius and 400 degrees Celsius.
 20. The method as claimed in any one of claims 1 to 17, wherein the reaction zone is disposed at a temperature of between 150 degrees Celsius and 300 degrees Celsius.
 21. The method as claimed in any one of claims 1 to 20, wherein the gaseous reagent material includes at least 40 mol % carbon tetrachloride, based on the total moles of the gaseous reagent material.
 22. The method as claimed in any one of claims 1 to 21, wherein, within the reaction zone, the ratio of moles of the carbon tetrachloride to moles of the target metallic material is at least 2.5.
 23. The method as claimed in any one of claims 1 to 22, wherein, within the reaction zone, the ratio of moles of the carbon tetrachloride to moles of the target metallic material is between 2.5 and
 5. 24. The method as claimed in any one of claims 1 to 23, wherein the solid material consists of the target metallic material and other material, and wherein the contacting effects production of a gaseous reaction product, wherein the ratio of moles of the target metallic material within the gaseous reaction product to moles of the other material within the gaseous reaction product is greater than the ratio of moles of the target metallic material within the solid material to moles of the other material within the solid material.
 25. The method as claimed in any one of claims 1 to 23, wherein the solid material consists of the target metallic material and other material, and wherein the contacting effects production of a gaseous reaction product, wherein the ratio of moles of the target metallic material within the gaseous reaction product to moles of the other material within the gaseous reaction product is greater than the ratio of moles of the target metallic material within the solid material to moles of the other material within the solid material by a multiple of at least
 2. 26. The method as claimed in any one of claims 1 to 25, further comprising separating from the gaseous reaction product, a target metallic material-rich product and a target metallic material-lean product, wherein the concentration of the target metallic material within the target metallic material-rich product is greater than the concentration of the target metallic material within the target metallic material-lean product.
 27. The method as claimed in any one of claims 1 to 25, further comprising separating, from the gaseous reaction product, a target metallic material-rich product and a target metallic material-lean product, based on differences in volatility as between the target metallic material-rich product and the target metallic material-lean product, wherein the concentration of the target metallic material within the target metallic material-rich product is greater than the concentration of the target metallic material within the target metallic material-lean product.
 28. The method as claimed in any one of claims 1 to 25, further comprising separating, from the gaseous reaction product, a target metallic material-rich product, based on differences in volatility as between the target metallic material-rich product and a residue, deriving from the gaseous reaction product, whose production is also effected by the separating, wherein the concentration of the target metallic material within the target metallic material-rich product is greater than the concentration of the target metallic material within the residue.
 29. The method as claimed in any one claims 1 to 28, wherein the separating, from the gaseous reaction product, of a target metallic material-rich product and a target metallic material-lean product includes cooling the gaseous reaction product so as to effect desublimation of at least a fraction of the gaseous reaction product and effect production of a desublimed product, and heating the desublimed product so as to effect sublimation of at least a fraction of the solidified reaction product and effect production of a sublimed product, wherein the sublimed product defines the target metallic material-rich product.
 30. The method as claimed in any one of claims 1 to 29, wherein the reaction zone is disposed at between 7 bar and 12 bar.
 31. A method of reducing niobium chloride comprising contacting niobium chloride with aluminium.
 32. A method of reducing tantalum chloride comprising contacting tantalum chloride with aluminium. 